Multiple applications require the generation of a signal with a variable oscillation frequency. For example, mobile telecommunication applications may require the use of digitally-controlled oscillators (DCO) or voltage-controlled oscillators (VCO) to support multiple frequency bands. A use case for a digitally-controllable, accurate synthesizer with a quickly varying output frequency may, for example, be the application within power efficient polar modulators for high bandwidth wireless standards, such as for example Long Term Evolution mobile telecommunication networks (LTE). Modulators or frequency synthesizers providing for a fast variation of the output frequency may be based on digitally-controlled oscillators so that their control may be performed in the digital domain. However, conventional approaches with analogue oscillator signals may face severe trade-offs between the static and the dynamic frequency tuning range, the maximum speed of modulation, phase noise, power, area and cross-coupling between multiple parallel paths. Hence, the applicability in advanced communication systems, as for example LTE with carrier aggregation is limited. Therefore, there may be a desire to provide for circuits, synthesizers and methods for synthesizing a signal with a selectable frequency with improved characteristics.